1. Field of the Invention
The present invention relates to a resilient crawler.
2. Description of the Related Art
An endless crawler vehicle to be used for civil engineering machines, construction machines, farm machines, snow mobiles and snow cars comprises a resilient crawler wrapped around a driving wheel, a following wheel, and a rolling wheel on a track frame.
The resilient crawler comprises a crawler body formed of a resilient material such as rubber in the shape of an endless belt, and the crawler body is constructed to be turned by an engaging transmitting system using a sprocket as a driving wheel, or by a friction transmitting system using a drum wheel.
The crawler body includes a lug for traction projecting from the outer peripheral surface at intervals along the longitudinal direction of the belt.
In a conventional resilient crawler of this type, core metals having laterally extending wings are buried at intervals longitudinally along the crawler in order to assure traction or to prevent coming-off of the rolling wheel from the crawler by enhancing rigidity in the widthwise direction of the crawler, i.e., lateral rigidity. However, such core metals increase weight and manufacturing cost of the resilient crawler.
Therefore, a technology in which cords such as wire extending in the direction of the width of the crawler body is buried in the lug instead of, or in addition to the core metal, whereby increasing lateral rigidity and avoiding or minimizing the use of core metals is disclosed in Japanese Examined Patent Publication No. HEI 8-11549 (hereinafter referred to as Related Art 1), Japanese Unexamined Patent Publication No. HEI 4-189688 (hereinafter referred to as Related Art 2).
In the resilient crawler of Related Art 1, a number of cords are buried only in the portions where the lugs are formed (within the lug), and they are not buried in the portions between the lugs.
Therefore, advantageously, lateral rigidity of the lug is enhanced and thus traction is ensured, and the portions between lugs can be bent smoothly when they comes around the driving wheel or the following wheel and thus possibility of occurrence of drive transmission loss can be reduced.
However, since the difference in rigidity between the portion where the lug is formed and the portion between the lugs is significant, the rolling wheel considerably sinks into the crawler body, thereby impairing riding comfort.
On the other hand, in Related Art 2, a resilient crawler having cords buried not only in the portion where the lug is formed, but also in the portion between the lugs is shown.
In this case, a multiplicity of cords are provided at regular intervals along the circumference of the crawler body both in the portion where the lug is formed and the portion between the lugs, and a multiplicity of these materials are provided also within the lug.
Therefore, since the number of the cords in the portion where the lug is formed is increased, the lateral rigidity of the lug is enhanced and the difference in rigidity between the portion where a lug is formed and the portion between the lugs is reduced in comparison with Related Art 1, whereby improvement in riding comfort can be realized.
However, since the cords are arranged at regular intervals both in the portions where a lug is formed and the portions between the lugs, when the intervals between the cords are decreased to increase the number of the cords so that rigidity of the lug is enhanced, the intervals of the cords in the portion between the lugs are also reduced and thus the number of the cords are increased. As a consequence, the flexibility of the crawler around the wheel is impaired, and the quantity of rubber between the lugs decreases, thereby increasing the possibility of occurrence of separation or cracking.
The lateral bending occurring on the resilient crawler is mainly caused by the load of the rolling wheel passing along and thus sinking the lateral center of the crawler body when the vehicle travels on a soft ground or on the snow. However, in Related Art 1 and 2, the cords are buried in almost uniform numbers along the width of the crawler body, and thus rigidity is also uniform along the width. Therefore, when rigidity of the lateral center of the crawler body, which contributes highly to the prevention of bending, is increased, rigidity of both side portions of the width of the crawler body, which contributes less to the prevention of bending, is also increased more than necessary, and thus the weight of the crawler is unnecessarily increased.
On the other hand, in Related Art 1, the cords having almost the same length as the lug are buried in the lug so as to be distributed throughout the lug from the foot portion, or the root of the lug projecting form the crawler body, and the volume proportion of the cords with respect to the lug is in the range between 20% to 70%. In other words, most part of the lug is filled with the cords.
In this state, a resilient material, which is a material forming the crawler body, cannot be sufficiently spread among the cords, and thus the thickness of the resilient material of the surface layer, or at the portion surrounding the cords, of the lug is decreased. As a consequent, separation or cracking may disadvantageously occur relatively easily between the cords or between the layers of the cords and the resilient material.
Even when they are the same in proportion of volume, lateral rigidity of the crawler varies depending on the position where the cords are buried, and thus variation in the position where the cords are buried may disadvantageously cause variation in tractive force, which may result in impairment of its original capability.
Accordingly, it is an object of the present invention to assure flexibility between the lugs and prevent separation of rubber while assuring lateral rigidity of the lug by properly disposing lateral reinforcing members in the crawler body without deteriorating riding comfort.
It is another object of the present invention to prevent increase in weight while effectively preventing lateral bending of the crawler body.
It is still another object of the present invention to increase durability by preventing occurrence of separation or cracking of the lug and to obtain a uniform tractive force by the lug.
The first specific means for solving the problems according to the present invention is a resilient crawler comprising: a crawler body formed of a resilient material in the shape of an endless belt and having a multiplicity of lugs projecting from its outer peripheral surface at intervals longitudinally along the crawler; and a multiplicity of lateral reinforcing members in the shape of cords extending laterally (in the widthwise direction) of the crawler body and arranged longitudinally along the crawler body; wherein the lateral reinforcing members are arranged at close intervals with respect to each other in each portion of the crawler body where the lug is formed, and at larger intervals with respect to each other in each portion between the lugs.
In this arrangement, since the difference in rigidity between the portion where the lug is formed and the portion between the lugs is reduced, riding comfort is expected to be improved, and the flexibility between the lugs can be assured and separation of rubber can be prevented while improving lateral rigidity of the lug and obtaining preferable traction.
The second specific means for solving the problems according to the present invention is a resilient crawler comprising: a crawler body formed of a resilient material in the shape of an endless belt and having a multiplicity of lugs projecting from its outer peripheral surface at intervals longitudinally along the crawler body; and a multiplicity of linear lateral reinforcing members extending laterally of the crawler body and arranged longitudinally along the crawler body; wherein the volume proportion of the lateral reinforcing members is high at the lateral center of the crawler body and low at the lateral outer portions of the crawler body.
In this arrangement, rigidity at the lateral center of the crawler body is further increased and thus lateral bending can be prevented, and volume proportion of the lateral reinforcing members near the lateral edges of the crawler is lowered and thus the increase in weight and cost can be prevented.
The third specific means for solving the problems according to the present invention is a resilient crawler comprising: a crawler body formed of a resilient material in the shape of an endless belt and having a multiplicity of lugs projecting from the outer peripheral surface at intervals longitudinally along the crawler body; and a multiplicity of linear lateral reinforcing members extending laterally of the crawler body and arranged longitudinally along the crawler body; wherein the lateral reinforcing members are arranged at close intervals with respect to each other in each portion of the crawler body where the lug is formed, and at larger intervals with respect to each other in each portion between the lugs, and wherein the volume proportion of the reinforcing members is high at the lateral center of the crawler body and low at the lateral outer portions of the crawler body.
Therefore, the same effect as the first and second means can be achieved simultaneously.
The fourth specific means for solving the problems according to the present invention is a resilient crawler of the second and third means, wherein a plurality of layers of reinforcing member each having a multiplicity of lateral reinforcing members longitudinally arranged in and along the length of the crawler body are provided in the thicknesswise direction of the crawler body, and wherein the lateral reinforcing members in each reinforcing member layer are different in lateral length from layer to layer and are centered laterally of the crawler body.
Therefore, arrangement of the lateral reinforcing members in such a manner that the volume proportion is high in the lateral center and low in the lateral outer portions of the crawler body can easily be realized.
A fifth specific means for solving the problems according to the present invention is a resilient crawler according to any one of the first to third specific means, wherein a plurality of layers of reinforcing member each having a multiplicity of lateral reinforcing members longitudinally arranged in and along the length of the crawler body are provided in the thicknesswise direction of the crawler body, and wherein the lateral reinforcing members in each reinforcing member layer are oriented to intersect with respect to neighboring layers.
By arranging the lateral reinforcing members in each reinforcing member layer so as to intersect with respect to neighboring layers, lateral rigidity can further be increased.
The sixth specific means for solving the problems according to the present invention is a resilient crawler of any one of the first to the third specific means, further comprising a circumferentially tensile belt-shaped member buried in the crawler body on the inner side of the lateral reinforcing members.
In this arrangement, circumferential expansion of the crawler body is controlled and occurrence of separation of rubber and cracking at the portion between the lugs may certainly be prevented.
The seventh specific means for solving the problem according to the present invention is a resilient crawler according to any one of the first to third specific means, wherein the lateral reinforcing members disposed at the portion of the crawler body where the lug is formed are arranged to form a curve in a cross sectional view in the widthwise direction of the crawler body so as to penetrate into the lug.
In this arrangement, lateral rigidity is effectively increased and a sufficient quantity of rubber of the lug is assured to prevent occurrence of separation or cracking.
The eighth specific means for solving the problems according to the present invention is a resilient crawler comprising: a crawler body formed of a resilient material in the shape of an endless belt and having a multiplicity of lugs projecting from the outer peripheral surface at intervals longitudinally along the crawler body; a resilient core portion formed of a resilient material provided in the core portion in the lug of the crawler body; and a multiplicity of linear lateral reinforcing members extending laterally of the crawler body and arranged longitudinally along the crawler body; wherein the lateral reinforcing members are arranged at close intervals with respect to each other at the portion of the crawler body where the lug is formed, and at larger intervals with respect to each other at the portion between the lugs; wherein the volume proportion of the lateral reinforcing members is high at the center and low at outer portions in the widthwise direction of the crawler body; and wherein the lateral reinforcing members provided in the portion of the crawler body where the lug is formed are arranged so as to fringe the outer periphery of the resilient core portion.
According to this arrangement, in addition to the same effect as the first to the second embodiments, provision of the lateral resilient core portion can prevent the lug from being filled with the lateral reinforcing members more than necessary, and thus the resilient material can sufficiently spread around the lateral reinforcing members, so that separation and cracking can be prevented from being occurred between the lateral reinforcing members and the resilient material.
The ninth specific means for solving the problems according to the present invention is a resilient crawler comprising: a crawler body formed of a resilient material in the shape of an endless belt and having a multiplicity of lugs projecting from the outer peripheral surface at intervals longitudinally along the crawler body; a resilient core portion formed of a resilient material provided in the core portion in the lug; and a multiplicity of lateral reinforcing members buried in the lug so as to fringe the outer periphery of the resilient core portion.
In this arrangement, the lug is prevented from being filled with the lateral reinforcing members more than necessary, and thus the resilient material can be sufficiently spread around the lateral reinforcing members, so that separation and cracking can be prevented from being occurred between the lateral reinforcing members and the resilient material.
In the ninth specific means, it is not specifically limited whether to bury the lateral reinforcing member along almost the whole circumference of the crawler body continuously or discontinuously, that is, whether to arrange the lateral reinforcing members circumferentially without intervals or to arrange the lateral reinforcing members at prescribed intervals so as to correspond to the portions between the lugs.
The tenth specific means for solving the problems according to the present invention is a resilient crawler of the ninth specific means, wherein a plurality of layers of reinforcing members each having a multiplicity of lateral reinforcing members longitudinally arranged along the length of the crawler body are provided in the thicknesswise direction of the crawler body.
In this arrangement, the volume proportion of the lateral reinforcing members with respect to the lug is increased within a proper range, which leads to increase in lateral rigidity both for the crawler body and for the lug.
The eleventh specific means for solving the problems according to the present invention is a resilient crawler of the ninth specific means, wherein the lateral reinforcing member is dispersed longitudinally of the crawler body at the positions corresponding to the edge of the lugs in the lateral direction of the crawler.
It means that the lateral reinforcing members are buried in a broad range exceeding the width of the lug in the lateral direction of the crawler body, and dispersion of the lateral reinforcing members longitudinally of the crawler body can enhance the integrity thereof with the lug and the crawler body, which leads to increase in lateral rigidity both for the crawler body and for the lug.
The twelfth specific means for solving the problems according to the present invention is a resilient crawler of the ninth specific means, wherein the volume-proportion of the lateral reinforcing member in the lug is 5% to 20%.
When the volume proportion is less than 5%, lateral rigidity to be provided by the lateral reinforcing members cannot be realized, and when it exceeds 20%, the adhesive force between the lateral reinforcing members and the resilient material becomes insufficient. Therefore, the volume proportion is preferably determined within the range described above.
The thirteenth specific means for solving the problems according to the present invention is a resilient crawler of the ninth specific means, wherein the lateral reinforcing members are buried in the lug so that L1/L and H1/H are each 30%-80%, where L is the width of the base portion of the lug, H is the height of the lug, L1 is the width of the base portion of the lateral resilient core portion, and H1 is the height of the lateral resilient core portion in the cross sectional view of the lug in the widthwise direction of the crawler body.
In this arrangement, the lateral reinforcing members can be buried at best positions.
When L1/L less than 30%, the adhesive force between the lug and the crawler body is too low, and when L1/L greater than 80%, the lateral reinforcing members come to the position immediately below the outer surface of the lug, which may cause separation. When H1/H less than 30%, sufficient lateral rigidity of the crawler body cannot be realized, and when H1/H greater than 80%, the lateral reinforcing members come to the position immediately below the force-bearing surface of the lug, which may result in breakage. Therefore, it is more preferable to set L1/L and H1/H within the range of 40% to 60%.
According to the ninth to thirteenth embodiments described above, the distribution of the lateral ground pressure of the lug on the crawler body is equalized and thus the tractive performance is significantly improved. In addition, since the crawler body can be made thinner and thus the bending rigidity at the portion of the crawler body wrapped around the wheel can be reduced significantly, the torque loss when being driven, or on traveling, is reduced, and accordingly, the resultant improvement of fuel consumption and the effect of push-pull resistance lead to the improvement of the traveling performance.
The fourteenth specific means for solving the problems according to the present invention is a resilient crawler of the ninth specific means, wherein the lateral reinforcing member is buried in the portion of the crawler body between the lugs so as to intersect the longitudinal direction of the belt.
In this arrangement, even when the volume proportion of the lateral reinforcing members in the lug is reduced, lateral rigidity of the crawler body increases.
When a pin-system is employed for driving the resilient crawler as the fifteenth specific means for solving the problems according to the present invention, it is recommended to employ a resilient crawler of the ninth specific means, wherein drive transmission projections to assist drive transmission are formed on the inner peripheral surface of the crawler body at the positions corresponding to the portions where the lugs are formed.
As the sixteenth specific means for solving the problems according to the present invention, it is recommended to employ a resilient crawler of the ninth specific means, wherein the lug includes a long lug having a longer length along the width of the crawler body and a short lug having a shorter length in the widthwise direction of the crawler arranged in a mixed manner at a specified proportion in the longitudinal direction of the crawler, and wherein the drive transmission projection is provided on the inner surface of the crawler body at the position corresponding to the portion where the long lug is formed.
In this case, the long lug and the part of the crawler body close to it is high in rigidity in comparison with that of the short lug as a matter of course because of its length, and the extent of generation of the tractive force, or driving force, of the long lug is larger than that of the short lug, whereby providing a drive transmission projection corresponding to the long lug is more logical.
The seventeenth specific means for solving the problems according to the present invention is a resilient crawler of the ninth specific means, wherein the tread surface of the lug is formed with a plurality of edge portions for preventing side skid arranged at a plurality of locations along the width of the crawler body with their longitudinal direction oriented along the longitudinal direction of the crawler body.
In this arrangement, a suitable countermeasure for side skid is taken, and thus it is especially useful for snowmobiles or the like in which employment of a lightweight resilient crawler is recommended.
The eighteenth specific means for solving the problems according to the present invention is a resilient crawler of the ninth specific means, wherein the crawler body is provided with a plurality of circumferential tensile members buried in the longitudinal direction thereof.
In this arrangement, expansion of the crawler body in the longitudinal direction is prevented and rigidity is increased.
The nineteenth specific means for solving the problems according to the present invention is a resilient crawler of the ninth specific means, wherein the resilient core portion is formed of a high-hardness rubber of at least 60xc2x0 in hardness (JIS Shore A-type).
The present invention provides a method of manufacturing a resilient crawler as set forth in the ninth specific means comprising the steps of: providing a vulcanizing die having a recess for molding belt shaped crawler bodies and a plurality of molding recesses for molding lugs formed along the longitudinally of the recess for molding crawler bodies so as to increase the depth of the crawler mold recess; filling the die with a resilient material and laying a plurality of linear lateral reinforcing members with their longitudinal direction oriented laterally of the recess for molding the crawler body so that the lateral reinforcing members are interposed between the resilient material like a sandwich; and carrying out vulcanization of this combination with the dies mated to obtain a crawler body comprising lugs with the lateral reinforcing members moved by melted resilient materials therearound to positions fringing the resilient core portions within the lugs.
In this way, the lateral reinforcing members can be buried in the lug so as to fringe the core portion with the core portion left as it is by means of flowing property of the resilient material at the time of vulcanization, whereby the structure of the resilient crawler as the ninth specific means can easily be manufactured.
The manufacturing method described above further comprises a step of subjecting the reinforcing member layer including a multiplicity of the lateral reinforcing members formed into almost the same length as that of the lug to the electron beam treatment before filling it into the vulcanizing die.
This eliminates variations, or unevenness, of movement of the lateral reinforcing members, and facilitates operation such as filling into the die.